They’re right to be worried. Particle levels in London may not be as high as China but they still average 50% over the World Health Organisation (WHO) guideline. In contrast, levels of nitrogen dioxide (NO2), a toxic gas, tend to be the highest in the world along many roads in central London, almost entirely due to diesel vehicles.

These horrifying statistics are very relevant to the London mayoral elections since the next mayor will control 100% of all vehicle emissions in London, but much less from buildings or any other policy area. Put starkly, the next mayor's job is to ban diesel vehicles from the most polluted places before the current generation of kids leaves school.

The best and fairest mechanism to achieve this transformation would be Emissions Based Road Charging (EBRC) to simplify the current congestion charging zone, low emission zone and so-called ultra-low emission zone (ULEZ) and put pollution at the heart of London's traffic management. This change would be self-funding.

Let's also raise up to £350m per annum for other transport improvements and to ease the transition from diesel, by scrapping the exemption from the congestion charge for minicabs that have doubled in number in recent years.

To keep things simple, we've developed a brutal, transparent and fair Clean Air Score of mayoral candidates that focuses on their powers to tackle the biggest problems. We're offering four points out of 10 to candidates who will tighten Boris’s ULEZ — which is too small, too weak and too late in 2020 — and use EBRC.

We don’t just need to ban diesel. We also want a positive revolution. So we’re offering one point each for: promises of political leadership; smog warnings; massive support for active travel and public transport; and investment in our electricity infrastructure. Candidates hit the jackpot with two extra points if they back our whole manifesto which includes a raft of smaller measures.

So far, Sian Berry (Green) scores a ‘Perfect 10/10’ after her clean air manifesto included everything we’d requested and more. Caroline Pidgeon (Liberal Democrat) is also scoring well (7.5/10) for supporting higher charges for diesel vehicles with some bans by 2024. We've not found anything significant by Peter Whittle (UKIP) on air pollution, other than opposing river crossings for cars, so he scores zero.

Sadiq Khan (Labour) scores 6/10 after promising to 'consult on bringing forward the ULEZ [from 2020] and expanding it along major arterial routes or a wider section of central London'. He will score better if he pledges smog warnings or promises to strengthen the ULEZ.

Last week, Zac Goldsmith (Conservative) pledged to 'consult with London councils and local communities on how the [ULEZ] can be strengthened... and ask local people living outside the current proposed area whether they want it in their area'. He will score better if he confirms implementation before 2020. So far, despite some excellent smaller promises, we've scored him 4.5/10.

The only way we can explain the difference between everyone’s expectations for Zac and his Clean Air Score is that ‘car is king’ Tories, who’ve stopped Boris from banning older diesel cars as Berlin did in 2010, are holding him back.

With one month to go, the London mayoral election should focus on the future of over 1m people exposed to illegal levels of NO2 and the health of a generation of schoolkids versus the future of tens of thousands of diesel vehicles. We need another Clean Air Revolution now.